recommended premium but not "required". The wrx prior to 2015 said this:

The engine is designed to operate using premium unleaded gasoline with an octane rating of 91 AKI (95 RON) or higher. If premium unleaded gasoline is not available, regular unleaded gasoline with an octane rating of 87 AKI (90 RON) or higher may be temporarily used. For optimum engine performance and driveability, it is required that you use premium grade unleaded gasoline.
NOTE
Be sure to use premium unleaded gasoline of 91 AKI (95 RON) or higher. If other gasoline (lower than 91 AKI (95 RON)) is used, knocking, reduced output and poor accelerator response will result.

recommended premium but not "required". The wrx prior to 2015 said this:

The engine is designed to operate using premium unleaded gasoline with an octane rating of 91 AKI (95 RON) or higher. If premium unleaded gasoline is not available, regular unleaded gasoline with an octane rating of 87 AKI (90 RON) or higher may be temporarily used. For optimum engine performance and driveability, it is required that you use premium grade unleaded gasoline.
NOTE
Be sure to use premium unleaded gasoline of 91 AKI (95 RON) or higher. If other gasoline (lower than 91 AKI (95 RON)) is used, knocking, reduced output and poor accelerator response will result.

FiST runs great on 87. The only time I felt it was in 3rd, one corner on the dragon. It felt a tad sluggish (a bit is used loosely). Overall, 93 really is not needed for performance. Best bet for FiST performance is lighter wheels and 225mm 200TW tires

FiST runs great on 87. The only time I felt it was in 3rd, one corner on the dragon. It felt a tad sluggish (a bit is used loosely). Overall, 93 really is not needed for performance. Best bet for FiST performance is lighter wheels and 225mm 200TW tires